chadjenofsky: I also prefer a bootable antivirus, but I think it even more safe if the boot-up and scan were done with the computer unplugged from the Internet. I once had to disinfect a PC that had a virus that was incredibly resilient unless there was no Internet connection. Then it became completely dormant as if to remain undetected.
timppu: Was the system booted to Windows? I think this is the reason at least Kaspersky Rescue CD uses some kind of Linux bootup.
The Avira AntiVir Rescue System bootable disk is Linux-based. Here's an
excerpt: The Avira AntiVir Rescue System a linux-based application that allows accessing computers that cannot be booted anymore. Thus it is possible to repair a damaged system, to rescue data or to scan the system for virus infections. Just double-click on the rescue system package to burn it to a CD/DVD. You can then use this CD/DVD to boot your computer. The Avira AntiVir Rescue System is updated several times a day so that the most recent security updates are always available. Also, there are directions on installing to a bootable USB stick
here using UNetbootin. This article also confirms that you can update the antivirus definitions via the Internet.